1. Field of the Invention
The present invention relates to a heating apparatus for an automotive vehicle, and more specifically to a heating system in which an ordinary heating apparatus for heating the vehicle room by warmed engine coolant and an additional heating apparatus for heating the same by engine exhaust gas are combined with each other.
2. Description of the Prior Art
An example of the heating system for an automotive vehicle in which an ordinary coolant-dependent heating apparatus and an additional exhaust gas-dependent heating apparatus are incorporated is disclosed in Japanese published Unexamined (Kokai) Patent Appli No. 59-16211, for instance.
In the prior-art heating system including an additional exhaust gas dependent heating apparatus; however, in case cracks or gaps are formed in the heating elements, for instance at the junction points between an evaporator pipe and an evaporator tank due to thermal fatigue or malsoldering, since medium vapor (e.g. steam) is jetted through the cracks or gaps and therefore the pressure drops down to the atmospheric pressure, there exists a problem in that the heating function of the additional heating apparatus is perfectly damaged.
In addition, in case cracks or gaps are formed at both the evaporator side and the condenser (i.e. heat exchanger) side, there exists a serious problem in that exhaust gas including carbon monoxide and introduced into the heat pipe is then discharged into the vehicle room.